Gallium is a grayish metal element that is denoted by the atomic symbol Ga. Its atomic number is 31 and its atomic weight is 69.723. It remains liquid over a larger range of temperatures--from its melting point of 85.6°F(29.76°C) to its boiling point of 3,999.2°F (2,204°C)--than almost any other metal. This property makes it useful in large temperature range thermometers.

When Dmitri Mendeleev announced his periodic law in 1869, he predicted the existence of three missing elements needed to fill empty spaces in the periodic table. Only six years later, the first of these elements was discovered but not, as one might expect, by someone who was primarily looking for Mendeleev's predicted elements. Instead, the element was found by Paul Émile Lecoq de Boisbaudran, who was studying the spectral lines of the metals.

Boisbaudran was one of the early pioneers of the science of...